Process for the thermal treatment of pulverulent material



F. BARTLING Nov. 11, 1930.

PROCESS FOR 'DHE THERMAL TREATMENT OF PULVERULENT MATERIAL Filed Feb.14, 1929 Patented Nov. 11, 1930 UNITED STA TENS-PATENT err-wa FRIEDRICHBARTLINGQOF mumcnfemmany'n Pnocnss FOR THE THERMAL TREATMENT orPULVERULENT MATERIA y Application filed February 14, 1929, Serial No.340,004, and in Germany February 2, 192a. 1

The invention relates to the thermal treatment of pulverulent material,and essentially is intended to prevent, or at least appreciably toreduce, the undesirable and previ- 8 ously unavoidable intimate mixingof the solid product with the gasifiedor otherwise,

gaseous products. I 1' Although the new mode of operation can be usedusefully with every kind of-mate- 10 rial in the form of veryfine'dust,dry distillation of pulverulent materials, whichplays such an importantpart in the industries con cerned, is the primary object. As. it isgenerally known that, for the purposes of dry distillation, theemployment of bituminous material ground to the fineness of dust affordsveryv considerable advantages, over the use of granular or lumpy piecesof material,

these advantages scarcely require explana- 80 tion. Here, however, it isbriefly stated that one appreciable advance due to working withpulverulent material resides primarilyin the possibility of a continuousoperation with shortest possible time of transit for completedistillation of the individual particles of the material, so that, asthe heat applied can readily permeate the material, a considerableeconomy in heat can be effected. This gives not only an absolutelyuniform product,- but also very valuable oils, because itis pos sible todry distill suchpulverulent material, by taking suitable precautions, atmuch lower temperatures than previously were possible.-

If the material for dry distillation has been ground to a fineness lyingbetween a sieve mesh of 31500 per sq. in. and 64500 per sq. in., then itis possible to feed it directly and without further grinding, to thedust furnace.

Such a fuel for the dust furnace is exceedingly cheap, because theextremely valuable oils are obtained as by-product, and has in additionthe reat advantage of being almost entirely smokeless.

This has already been appreciated by the industries concerned, andconsequently attention paid to the problem of carrying out a drydistillation process in which the material, whether coal, lignite, peator an other known fuel, is distilled in the form 0 a very in a stream ofheated fine powder, It was I immediately realised that itfis notpossible to d ry distillsuch fine powders in the form: of compactmasses,and

thus came the process of suspending the dust;

gas, and t'hu s to..dry" distill suspended particles. Thisproeess is, initself, effective, but sufiersfrom the serious drawback'of all dust 'distillationa'that the separation of the gaseous products and, fuel dustcannot beeflected completely and 9 even the partial separation isattended bydifficulties.

The conception underlying the p lsent j 'venti'on is that such adustdistillation proc- 'iss can be more eifect'ively carried out if theliulyerulent material is spread out in the thinnest possible layer on ahearth surface trave ling through the distillation chamber; B7,. thismeans, provided thatthe layer issufiim ntly thin, the distillationprocess can be carried out very: thoroughly,- very uniformly and withthe applicatioriof very little heat; But it is immediately clear thatthe defect of the process of distillation of'suspended dust part'icles,viz. the intimate mixing of the gaseous and solid products ofdistillation, is likely to occur to some extent here also, and can onlybe avoided when it is possible to prevent any of the pulverulentmaterial distributed over, the working surface from being taken up intosuspension. I f y The solution of this problem presentedvseriousdifficulties a-nd the subject of the present invention is intended toconstitute a means for attaining this obj ect,.but.as already 8 stated,the application of the present process is not limited to dry.distillation of dust, but the. basic process can also be applied to thethermal treatment of pulverulent material of every kind.

According to the invention, the solution of the particular problem 'setoutabove resides in the utilization of electrostatic adhesion.

The basic idea of the invention isthe vutil-ization of these Knownhysical phenomena for the solution ofthe aiiove problem. v

Consequently the invention comprises a process for the thermal treatmentof pulve'ruent material on a travelling workin surface characterized inthat the materia on the nd be insulated from the other Parts of thefurnace. A friction device, such as brushes of-the like, past which themovingworking surface travels, may serve to generate the weak"electrostatic charge. The material is laid'ft on the working surface ina thin layer andj 'immediately adheres to it. The adhesion is strongenough to prevent the pulverulent'material from being whirled away I.,-but is not so powerful that, at the point where the material iscollected, the powder cannot V be scraped off, for example by a knife ofnonconducting material. This scraper device must, of course, beseparated as far as possible in a dust-tight manner from the workingchamber. The separation is facilitated as, due to the electric adhesion,the dust-layer still adheresto the Working surface when the latter is inan inverted position. If, for exam le, an endless metal band carried onrol ers is used as travelling hearth plate, the collectin point canbe'situated on the under J 100p of t 1e endless band, which can readily"bein be separated from the furnace chamber above in a dust-proofmanner. 'It is obvious that other suitable collecting arrangements mayalso be utilized.

One illustrative form of an apparatus for performing such a process isset forth on the v accompanying drawings, in which:

Figure 1 is a vertical sectional view through the furnace.

Fig. 2 is a transverse sectional view through the furnace.

Fig. 3 is a top plan view of the furnace.

In these drawings, the furnace chamber is rovided with an endless metalconveyor and 1 assing over the two insulatin drums 2, which rotateclockwise as indicate by the arrows in Fig. 1. The drums and band arecaused to move by power applied at the pulley 3. A hopper 4 18 arrangedabove the conveyor band, and through it the pulverulent material ma befed onto the metal band, sprea out in a thin layer over the ban' andcarried along'thereon in the upper flight, and finall being dischargedat the right hand end 0 the machine in- Fig. 1, the band being utimatelycleaned by a scra er 5: the separated material falls downwar in a chuteand is drawn off through the discharge pipe 6. Between the two drums 2for pipe 11.

gases are withdrawn throughthe-discharge. i. V

' The heating thus effected causes a dry dis-.

tillation of the particles of pulverulent dry 1 material disposed in athin layer upon the upper flight of the band 1, and the gases and vaporthus deposited are collected in the space above theband and aredischarged through the pipes 12.

The new process can be utilized with furnaces and heating arrangementsof every kind, in so far as they are provided with a travelling hearthplate, and, for example, in addition to the furnace with hearth in theform of a band as already mentioned, with rotary annular plate furnacesand similar devices.

The application of an electrostatic charge to the working hearth doesnot prevent the lent solid carbonizable material which com risesdistributing the material in a thin ayer upon a traveling surface,holdin said material to said surface electrostatically by an electriccharge on said surface, and subjecting the material simultaneouslytherewith to destructive distillation while the said material isadherent-to saidsurface.

In testimony whereof I have signed my name to this specification.

FRIEDRICH BARTLING.

provision of devices on this latter, which by

